Bimetal indicator device with a heater energized under all operative conditions



BIMBTAL INDICATOR DEVICE WITH A HEATER ENERGIZED UNDER ALL OPERATIVE CONDITIONS Filed Jan. 26, 1965 8, 1967 J CANADAY 3,335,243

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A TTO-RNE Y United States Patent 3,335,243 BIMETAL INDICATOR DEVICE WITH A HEATER ENERGIZED UNDER ALL OPERATIVE CONDI- TIONS Joe R. Canaday, Anderson, Ind., assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Filed Jan. 26, 1965, Ser. No. 428.119 2 Claims. (Cl. 200-422) This invention relates to electric switches and more particularly to indicating devices for use with vehicle cooling systems.

It is an object of the present invention to provide an improved electric switch that utilizes a heated bimetal maintained at an equilibrium temperature by fluid in a cooling sysem for an engine.

It is another object of the present invention to provide an improved temeprature sensitive device which provides a visual indication of a temperature in an engine cooling system.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

FIGURE 1 illustrates the subject invention in its operative environment;

FIGURE 2 is a sectional view of the subject invention illustrated in an actuated position;

FIGURE 3 is a sectional view of the subject invention illustrated in a poised position.

Referring now to FIGURE 1, the subject invention, generally designated by the numeral 10, is shown operatively disposed through a wall 12 enclosing the cooling system of an engine. A typical storage battery 14 is connected to a terminal 16 of the switch through an ignition switch 18. An indicating lamp 20 is connected between a terminal 22 of the switch 10 and ignition switch 18 by line 23.

Referring now to FIGURE 2, the switch 10 or support means, as herein described, generally comprises a terminal support portion 24, a threaded wall portion 26 and an encapsulating cup-shaped member 28. The terminal support portion 24 is comprised of an insulating material of any well-known type while the threaded wall portion 26 and the cup-shaped member 28 are composed of conductive material. The threaded wall portion 26 has a seat portion 30 insulatedly carrying the cup-shaped member 28 compressed between the seat portion 30 and -a flange 32 bearing against a shoulder 34 of the terminal support portion 24. Resilient pads 36, compressed between the support portion 24 and the seat 30 as previously described, maintain the interior chamber 38 moisture-tight.

The terminal 16 conductively engages a plug 40' which is pressed into an aperture 42 in the support portion 24. Lacquer filler 44 is inserted into the plug 40, said lacquer filler 44 receiving a conductive member 46. The plug 40 can also be of rubber construction.

A bimetallic element 48 is operatively held by opposed wall portions 50 of the cup-shaped member 28. Contactor end 52, of the bimetallic element 48 is illustrated in FIG- URE 2 as being disposed against a conductive threaded plug 54 received in a plug 56 that is carried in an aperture 58 of the terminal support portion 24. It is seen that the terminal 22 conductively engages the plug 56. The conductive member 46 engages a heater 60 wrapped around the bimetallic element 48 and conductively engaging it at one extremity. A shield or sleeve 62 peripherally engages the threaded wall portion 26 on the lower end and provides protection for the cup-shaped member 28 against surges of fluid flow in a fluid chamber 64.

An examination of FIGURE 2 shows a path for current flow from the battery 14, through the ignition switch 18 to the terminal 16, through the plug 40, through the conductive member 46 to the heater 60. It is also seen that the heater 60 is grounded through the bimetallic element and the cup-shaped conductive member 28. Another path for current flow is established through the bimetallic element 48, through the plug 54, the plug 56 and the terminal 22 to the light 20. It is therefore seen that the heater 60 is energizable when the contact end 52. of the bimetallic element 48 is separated from the threaded plug 54. If the bimetal 48 deflects into engagement with the threaded plug 54, the heater remains energized and current flow will also go through the light 20, terminal 22, bimetal 48 to ground causing the light to become luminous.

In operation, the switch body 10 is inserted in any desired location in a passage carrying fluid whose temperature is to be monitored. Such an installation might be through the water jacket of an automobile engine. The light 20 would be positioned in the drivers compartment of the vehicle wherein it is visible to the vehicle operator. Normally, the disposition of the bimetal 48 is as shown in FIGURE 3. In this position, the heater 68 becomes energized when the ignition switch 18 is closed. Water in the chamber 64 engulfs the cup-shaped member 28 imparting its temperature thereto. The temperature of the member 28 is freely transmitted to the bimetal 48 and the heat generated therein by the heater 60 is therefore dissipated. In the normally designed control range of 0 to 240 F., suflicient cooling will be supplied to the bimetallic element 48 by the fluid to maintain the bimetal in an undeflected condition. It is understood that the control range of 0 to 240 F. is illustrative alone. A particular bimetal could be provided which is responsive to any temperature range.

Referring to FIGURE 2, if the fluid level drops to a point below the sleeve 62 and, consequently, below the opposed wall portions 50, the heat from the heater 60' cannot be so freely dissipated as when the fluid surrounds portions of the switch body. When this situation occurs, the heat from the heater 60 causes the bimetal 48 to deflect into engagement with the threaded plug 54. As previously stated, the current will flow through the light 20 to the grounded switch body. The associated mechanism can be designed so that suflicient heater voltage is maintained during a period when the light 20 is illuminated to maintain the bimetal in a deflected condition or an intermittent opening of the circuit to the light 20 could be provided to obtain a blinking light 20'. It is understood that a lowering of the fluid below the switch body is equivalent to a raising of the cooling temperature above the desired range because either circumstance would prevent sutficient heat dissipation from the bimetal 48. Therefore, the subject invention is responsive to -a coolant temperature as well as total loss of the coolant from the system.

The utility of the subject invention is clear in the environment of the cooling system of a vehicle engine. A need is had in that environment to provide an operator of a direct reading instrument for determining the condition of the coolant system. It is common in vehicles of present day design to have an indirect reading through a thermocouple placed in an engine block. However, with this arrangement, a lag can occur between the time the coolant is overheated and the block heats sufliciently, and localized heating in areas of the block not protected by thermocouple can develop with consequent destructive effects thereto.

While the embodiment of the present invention, as herein dis-closed, constitutes a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. An indicating device for a fluid system, said device comprising: a support element having a hollow interior and a threaded portion adapted to be threaded into the wall of a fluid carrying system so that a portion of said support element is disposed in fluid therein; a first terminal insulatedly carried by said support element and including a conductive path to the hollow interior of said support element, said first terminal conductively engaging an electrical power source; a second terminal engaging an indicating means and being insulatedly carried by said support element, said second terminal including a fixed contact means extending into the hollow interior of said support element; thermal responsive contact means carried by said support element and conductively engaging said first terminal, said contact means being carried in juxtaposition to the fixed contact means of said second terminal and being deflectable into engagement therewith in response to a disruption of a temperature equilibrium between the contact means and the fluid surrounding said support element; and heater means thermally and electrically conductively engaging said contact means to form a first circuit for raising the temperature of said contact means to a point which is normally offset by the temperaure of the fluid thereby maintaining the deflectable contact means away from the fixed contact means, said contact means being deflectable into conductive engagement with the fixed contact means to complete a second electrical circuit to the indicating mean-s while maintaining the first circuit energized when the fluid disposed around the support element is at a temperature wherein the temperature equilibrium between the contact means and the fluid is not maintained within predetermined limits, said support element including a substantially cylindrical shield surrounding the portion thereof disposed in the fluid carrying system a spaced distance from said support element thereby preventing the flow force of the fluid in the fluid carrying system from acting on said portion of the support element.

2. A fluid level and temperature sensing system comprising: a switch body adapted to be inserted through a wall of a fluid carrying system; in thermal and electrical conductive relationship therewith, said Wall being an electrical ground; an extension from said switch body extending into an area of said fluid carrying system wherein fluid is normally disposed in thermal conductive relationship with fluid in said fluid carrying system and in electrically conductive relationship with said switch body; bimetallic element carried by said extension in thermal and electrical conductive relationship therewith; heater means wrapped around said bimetallic element tob ring about a heating thereof; a plurality of terminal means insulated carried in one wall of said switch body, one of said terminal means providing a path for current flow between a power source and said heating means, said bimetallic element completing the circuit from said heating means to the grounded switch body under all operating conditions, another of said terminals providing a path for electrical current flow from an electrical current source and an indicating lamp to a conductive element disposed Within said switch body, said bimetallic element being deflectable into said conductive element disposed in said switch body when a predetermined amount of heat is retained by said bimetallic element; and shielding means carried by a portion of said switch body extending into the fluid carrying passage and substantially surrounding the extension of said switch body extending into said fluid carrying passage, a circuit normally being established through the heater means surrounding said bimetallic element providing a predetermined amount of heat input which is normally dissipated by fluid coming into contact with the exterior of said extension maintaining said bimetallic element out of en gagement with said conductive element, said bimetallic element being deflectable into said conductive element when heat generated therein by said heater means is not dissipated by the fluid in the fluid carrying system to complete a circuit between the power source and the indicating lamp through the bimetallic element to the grounded switch body alerting one monitoring the condition of the fluid carrying system of a heat buildup therein beyond predetermined limits, said bimetallic element concurrently providing a path for current flow through said heater means and said indicating lamp under conditions when an overheat condition is present in said fluid carrying system.

References Cited UNITED STATES PATENTS 2,507,365 5/1950 Boddy 200-138 2,613,294 10/1952 McNea ZOO-84 2,619,566 11/1952 Mahoney 200122 2,759,066 8/1956 Short et al. 200138 2,891,127 6/1959 Trarnontini 200-138 3,221,125 11/1965 Young 200-138 BERNARD A. GILHEANY, Primary Examiner.

H. A. LEWITTER, Assistant Examiner. 

1. A INDICATING DEVICE FOR A FLUID SYSTEM, SAID DEVICE COMPRISING: A SUPPORT ELEMENT HAVING A HOLLOW INTERIOR AND A THREADED PORTION ADAPTED TO BE THREADED INTO THE WALL OF A FLUID CARRYING SYSTEM SO THAT A PORTION OF SAID SUPPORT ELEMENT IS DISPOSED IN FLUID THEREIN; A FIRST TERMINAL INSULATEDLY CARRIED BY SAID SUPPORT ELEMENT AND INCLUDING A CONDUCTIVE PATH TO THE HOLLOW INTERIOR OF SAID SUPPORT ELEMENT, SAID FIRST TERMINAL CONDUCTIVELY ENGAGING AN INDICATTRICAL POWER SOURCE; A SECOND TERMINAL ENGAGING AN INDICATING MEANS AND BEING INSULATEDLY CARRIED BY SAID SUPPORT ELEMENT, SAID SECOND TERMINAL INCLUDING A FIXED CONTACT MEANS EXTENDING INTO THE HOLLOW INTERIOR OF SAID SUPPORT ELEMENT; THERMAL RESPONSIVE CONTACT MEANS CARRIED BY SAID SUPPORT ELEMENT AND CONDUCTIVELY ENGAGING SAID FIRST TERMINAL, SAID CONTACT MEANS BEING CARRIED IN JUXTAPOSITION TO THE FIXED CONTACT MEANS OF SAID SECOND TERMINAL AND BEING DEFLECTABLE INTO ENGAGEMENT THEREWITH IN RESPONSE TO A DISRUPTION OF A TEMPERATURE EQUILIBRIUM BETWEEN THE CONTACT MEANS AND THE FLUID SURROUNDING SAID SUPPORT ELEMENT; AND HEATER MEANS THERMALLY AND ELECTRICALLY CONDUCTIVELY ENGAGING SAID CONTACT MEANS TO FORM A FIRST CIRCUIT FOR RAISING THE TEMPERATURE OF SAID CONTACT MEANS TO A POINT WHICH IS NORMALLY OFFSET BY THE TEMPERATURE OF THE FLUID THEREBY MAINTAINING THE DEFLECTABLE CONTACT MEANS AWAY FROM THE FIXED CONTACT MEANS, SAID CONTACT MEANS BEING DEFLECTABLE INTO CONDUCTIVE ENGAGEMENT WITH THE FIXED CONTACT MEANS TO COMPLETE A SECOND ELECTRICAL CIRCUIT TO THE INDICATING MEANS WHILE MAINTAINING THE FIRST CIRCUIT ENERGIZED WHEN THE FLUID DISPOSED AROUND THE SUPPORT ELEMENT IS AT A TEMPERATURE WHEREIN THE TEMPERATURE EQUILIBRIUM BETWEEN THE CONTACT MEANS AND THE FLUID IS NOT MAINTAINED WITHIN PREDETERMINED LIMITS, SAID SUPPORT ELEMENT INCLUDING A SUBSTANTIALLY CYLINDRICAL SHIELD SURROUNDING THE PORTION THEREOF DISPOSED IN THE FLUID CARRYING SYSTEM A SPACED DISTANCE FROM SAID SUPPORT ELEMENT THEREBY PREVENTING THE FLOW FORCE OF THE FLUID IN THE FLUID CARRYING SYSTEM FROM ACTING ON SAID PORTION OF THE SUPPORT ELEMENT. 